(1) Field of the Invention
The present invention relates to a semiconductor wafer separating method for joining a dicing tape to a semiconductor wafer to which a supporting member is joined via a double-faced adhesive sheet, fixing the resultant to a dicing frame, and separating the semiconductor wafer integrally with the dicing frame from the supporting member, and to a separating apparatus used for the method.
(2) Description of the Related Art
In resent years, with rapid progress of an application, reduction in thickness of a semiconductor wafer to 100 μm to 50 μm, in some occasions, even to 25 μm is demanded. Such a thin semiconductor wafer is brittle and easily distorted and its handling is extremely difficult. Consequently, the semiconductor wafer is held by being joined to the surface side of a supporting member having strength such as a glass plate via a both-faced adhesive sheet. After the semiconductor wafer is reinforced by backing with the supporting member as described above, the back grind process is performed on the back face of the semiconductor wafer, and the semiconductor wafer is separated from the supporting member.
Hitherto, means for separating a semiconductor wafer held by being joined to a supporting member via a both-faced adhesive sheet is performed as follows. A both-faced adhesive sheet of an ultraviolet curing type whose adhesive strength is weakened by irradiation with an ultraviolet ray is used. First, by irradiation with ultraviolet rays, the adhesive strength is preliminarily decreased. In the subsequent process, the semiconductor wafer is sandwiched by upper and lower two tables and heated in a vacuumed state so as to be shrink-deformed, thereby reducing the contact area between the both-faced adhesive sheet and the semiconductor wafer, and the semiconductor wafer is floated.
After completion of the shrinking and separation of the both-faced adhesive sheet, suction of the upper table is cancelled and the upper table is withdrawn to the upper side. After that, in a state where the semiconductor wafer is suction-fixed on the lower table, a holding member is sucked and moved by a transport arm, thereby separating the semiconductor wafer from the both-faced adhesive sheet. Such means is proposed and carried out (see, for example, JP-A 2001-7179).
As the both-faced adhesive sheet used, not only a both-faced adhesive sheet of the ultraviolet curing type but also a both-faced adhesive sheet having heating separability which foams when heated and whose adhesive strength decreases are used.
The conventional means has the following problems.
In the case where a both-faced adhesive sheet has heating separability such that the sheet foams when being heated and its adhesive strength disappears, if a semiconductor wafer is restrained by being sandwiched by upper and lower two tables, foaming (expansion) of the both-faced adhesive sheet is disturbed and the adhesive strength cannot be sufficiently reduced. As a result, a problem occurs such that the semiconductor wafer cannot be smoothly separated from the supporting member.
For example, when the both-faced adhesive sheet whose adhesive strength has not disappeared is separated together with the supporting member from the semiconductor wafer, there is a possibility in that local separation stress acts on the semiconductor wafer and a warp or breakage may occur. There is also a problem that an adhesive remains on the surface of semiconductor wafer.